Process for producing water glass foams from aerosol containers

ABSTRACT

A process for producing in situ foams based on alkali metal silicates characterized in that an aqueous alkali metal silicate solution on the one hand and a hardener solution on the other hand are accomodated in separate pressurized containers A and B, prior to use the hardener solution in container B is added to and mixed with the silicate solution in container A in the presence of a suitable emulsifier for foam formation and a propellent gas liquid under high pressure between 0° and 50° C., and, on actuation of the discharge valve of container A, an alkali metal silicate foam is discharged. The alkali metal silicate foams formed are distinguished by non-inflammability, high temperature stability and good heat-insulating properties and are used as a filling, construction and insulating material or the like in the building industry.

BACKGROUND OF THE INVENTION

This invention relates to a process for producing foams based on alkali metal silicates by mixing the foam-forming components originally present in two separate pressurized containers and expelling the waterglass foam by means of a propellent gas liquefied under pressure at room temperature.

Various methods and various propellents and hardening agents for producing waterglass foams are described in the Patent literature. In this connection, a distinction has to be drawn between two fundamentally different procedures: on the one hand, chemical foaming where the propellent is formed for example by the decomposition of peroxides, preferably H₂ O₂, by metal powders or other reducing agents (DE-OS No. 22 27 640) or by the decomposition of carbides in aqueous solution (DE-OS No. 22 26 841); on the other hand, physical foaming where foaming is obtained by the injection of gases, for example air (DE-OS No. 20 39 736), or by heating (DE-OS No. 29 48 778).

Both procedures require elaborate machinery for metering and mixing several components (waterglass solution, hardener, propellent). Although they are suitable for the production of silicate foam products on an industrial scale, they are not really suitable for the production of silicate foams in situ, i.e. on site in the building industry for example. However, it is precisely in that field where silicate foams could be effectively used by virtue of their undisputed advantages over organic polymer materials (better temperature resistance without releasing toxic gases or smoke, non-inflammability, better processibility for the same insulation and construction properties). Above all, there is no known method for the simple production of in situ waterglass foams.

OBJECTS OF THE INVENTION

An object of the present invention is to overcome the deficiencies of the prior art and develop a simple method of in situ waterglass foam production.

Another object of the present invention is the development of a process for producing in situ foams based on alkali metal silicates comprising (1) mixing an aqueous alkali metal silicate solution, with a propellent gas which is liquid under pressure between 0° and 50° C., under sufficient pressure to maintain said propellent gas in liquid state, (2) just prior to foaming, adding to said aqueous alkali metal silicate solution a hardener solution while maintaining or increasing said pressure, (3) mixing said aqueous alkali metal silicate solution and said hardener solution in the presence of a suitable emulsifier for foam formation, and (4) applying said mixture of step (3) to a surface whereby said propellent gasifies on release of said pressure forming an in situ foam based on alkali metal silicates, where the amount and type of said hardener is so selected that the "pot life" of said mixture of step (3) before hardening is longer than the time required to apply all of said mixture of step (3) to a surface.

A further object of the present invention is the development of a process for producing in situ foams based on alkali metal silicates characterized in that an aqueous alkali metal silicate solution on the one hand and a hardener solution on the other hand are accomodated in separate pressurized containers A and B, prior to use the hardener solution in container B is added to and mixed with the silicate solution in container A in the presence of a suitable emulsifier for foam formation and a propellent gas liquid under high pressure between 0° and 50° C., and, on actuation of the discharge valve of container A, an alkali metal silicate foam is discharged.

These and other objects of the invention will become more apparent as the description thereof proceeds.

DESCRIPTION OF THE INVENTION

The present invention relates to a process for producing in situ foams based on alkali metal silicates characterized in that an aqueous alkali metal silicate solution on the one hand and a hardener solution on the other hand are accomodated in separate pressurized containers A and B, prior to use the hardener solution in container B is added to and mixed with the silicate solution in container A in the presence of a suitable emulsifier for foam formation and a propellent gas liquid under high pressure between 0° and 50° C., and, on a actuation of the discharge valve of container A, an alkali metal silicate foam is discharged.

More particularly, the present invention relates to a process for producing in situ foams based on alkali metal silicates comprising (1) mixing an aqueous alkai metal silicate solution, with a propellent gas which is liquid under pressure between 0° and 50° C., under sufficient pressure to maintain said propellent gas in liquid state, (2) just prior to foaming, adding to said aqueous alkali metal silicate solution, a hardener solution while maintaining or increasing said pressure, (3) mixing said aqueous alkali metal silicate solution and said hardener solution in the presence of a suitable emulsifier for foam formation, and (4) applying said mixture of step (3) to a surface whereby said propellent gasifies on release of said pressure forming an in situ foam based on alkali metal silicates, where the amount and type of said hardener is so selected that the "pot life" of said mixture of step (3) before hardening is longer than the time required to apply all of said mixture of step (3) to a surface.

The principle underlying the invention is to emulsify a gas which is liquefied under pressure between 0° and 50° C., preferably at room temperature, in an aqueous waterglass solution in an aerosol container A and to force the hardener component into the container A by excess pressure in order to initiate the hardening reaction. Preferably the hardener component is contained in a separate container B.

The container B may also be an aerosol container or a special plastic container and, in addition, may be accommodated as an inner container in the aerosol container A in accordance with EP A No. 0 042 128. In this case, the hardener is transferred to container A by turning a spindle or by actuating a special valve. After the waterglass solution, propellent and hardener have been emulsified by shaking the container as a whole, the physical foaming process is initiated by actuating the aerosol valve to expel the mixture and to vaporize the liquefied gas serving as propellent. At the same time, the hardening reaction which begins after some delay results in solidification of the foam. The foam acquires its ultimate strength through physical hardening (release of water).

Sodium silicate and/or potassium silicate solutions are preferably used for producing the waterglass foams.

Alkali metal silicate solutions in which the molar ratio of SiO₂ to Na₂ O amounts to between 2 and 4:1 and preferably to between 2.5 and 3.5:1 or the molar ratio of SiO₂ to K₂ O to between 2.8 and 4:1 and preferably to between 3.2 and 3.5:1, are used in the process according to the invention. The total solids content of the solution amounts to between 27% and 50% by weight, so that the solution at 20° C. has a density of from 1.25 to 1.60 g/cc and a viscosity of from 10 to 5000 mPa.s and preferably from 50 to 1000 mPa.s. To improve the mechanical strength of the foams formed, quaternary ammonium compounds, borates and/or synthetic resins and also alkali-compatible organic and/or inorganic compounds may optionally be added to the alkali metal silicate solutions. Commercially available synthetic resin dispersions, such as for example styrene-acrylate dispersions, styrene-butadiene dispersions or polymers containing vinyl acetate, are preferably used for this purpose.

Hardeners suitable for use in accordance with the invention may be both organic and inorganic, liquid or gaseous. Suitable organic hardeners include, in particular, esters which split off acids under the effect of alkalis, such as glycerol triacetate for example. The dimethyl esters of oxalic acid, succinic acid, glutaric acid and adipic acid may also be used as hardeners, although they give waterglass foams of lower strength. In admixture with glycerol triacetate, they may be used for regulating the "pot life", i.e. the period of time elapsing between addition of the hardener to the silicate solution and hardening. Oxides or salts of polyvalent cations, for example zinc, magnesium or calcium, may also be added to the carboxylic acid esters. For example, zinc oxide may be used for this purpose.

In principle, it is also possible to introduce the hardener component into the alkali metal silicate solution in microencapsulated form. Microcapsules soluble in alkalis or in the propellent guarantee release of the hardener component when used in accordance with the invention.

In the preferred embodiment of the invention, however, the hardener component is accommodated in one of the two pressurized containers, for example an aerosol container. The hardener component is added to the alkali metal silicate solution using a propellent or propellent mixture which is gaseous above 0° C. and preferably at room temperature, for example nitrogen or carbon dioxide. In addition, this hardener/propellent combination may be mixed with a propellent which is liquefied under high pressure between 0° and 50° C. and preferably at room temperature.

A propellent is also used for expelling the alkali metal silicate/hardener mixture from the pressurized container A in the application of the waterglass foams in accordance with the invention. The propellent in question must be resistant to hydrolysis and alkalis and may consist of any of the propellents normally used for this purpose, for example dichlorodifluoromethane, dimethyl ether, propane/butane, optionally together with additions of other propellents, for example trichlorofluoromethane.

To carry out the process in accordance with the invention, it is particularly important uniformly to distribute or emulsify the propellent and the hardener in the aqueous phase. To this end, special emulsifiers have to be added to the waterglass/propellent/hardener mixture. Suitable emulsifiers are emulsifiers which are stable to alkalis and which, when mixed with waterglass, do not produce any increase in viscosity in the waterglass or any precipitations (gel formation) in the waterglass. An emulsion should be formed without any thickening when the aerosol container is shaken to mix the waterglass solution with the other components. According to the invention, the emulsifiers required for foam formation may be present in the pressurized container A and/or in the pressurized container B. To this end, they must be compatible with the alkali metal silicate solution, the hardener and the propellent gas and should not cause any precipitations in the alkali metal silicate system.

The emulsifiers used are nonionic, anionic, cationic and/or amphoteric surfactants (surface active compounds) known per se. Preferred emulsifiers are adducts of fatty alcohols with ethylene oxide, for example adducts of oleylcetyl alcohol with from 2 to 5 mols of ethylene oxide, quaternary ammonium salts containing one or two linear C₁₂₋₁₇ alkyl radicals, such as distearyl dimethyl ammonium chloride or lauryl trimethyl ammonium chloride, also monoesters of sulfosuccinic acid with tallow fatty acid monoethanolamide.

The silicate foams obtained by the process according to the invention are distinguished by high thermal stability (up to 300° C.) after hardening. According to DIN 4102, they are class A 2 building materials (noninflammable building materials). The thermal conductivity of various air-dry silicate foams hardened at room temperature amounted to between 0.043 and 0.068 w/m.K, depending upon the gross density of the foam and its moisture content.

The process according to the invention is illustrated by the following Examples which are to be deemed limitative in any respect.

EXAMPLES A. Description of the process

The waterglass solution, emulsifier, propellent and, optionally other additives according to the invention were introduced into an aerosol container to form component A.

The hardener and, optionally, other additives according to the invention were introduced into a second aerosol container and adjusted with nitrogen to a pressure of approximately 10 bars (component B).

After hardener component B had been injected into component A, the contents of both container were shaken by hand for about 1 minute, thereby homogenizing the reaction mixture. In the period of time elapsing between the end of shaking and the beginning of hardening (pot life), the foam-forming reaction mixture could be expelled from the aerosol container through a lever-operated valve.

The composition of the mixtures according to the invention and the pot lives and gross densities obtained are shown in the following Examples.

The following emulsifiers were used in the process according to the invention;

Emulgin 0 2 oleyl-cetyl alcohol +2 mols of EO

Emulgin 0 5 oleyl-cetyl alcohol +5 mols of EO

Elfanol 510 sulfosuccinic acid monoester with tallow fatty acid monoethanolamide

Dehyquart C lauryl pyridinium chloride

Dehyquart DAM distearyl dimethyl ammonium chloride

Dehyquart LT lauryl trimethyl ammonium chloride

B. Assessment criteria

1. Foam formation

If little or no foam was formed on discharge of the product from the aerosol can, foam formation was rated as "-". Satisfactory to very good foam formation was rated as "+".

2. Foam stability

Foam stability characterizes the possible collapse of the fresh, unhardened foam and is defined as the period of time in which no significant collapse of the foam could be observed (i.e. ≦10% reduction in volume).

    ______________________________________                                         Foam stability   rating                                                        ______________________________________                                         <5 minute        -                                                             >5 <15 minutes   +                                                             >15 <30 minutes  ++                                                            >30 minutes      +++                                                           ______________________________________                                    

3. Foam structure

The structure of the foam after hardening and drying (approximately 3 days at 25±5° C. ) was visually assessed. A fine-cell foam structure was rated as "+", a coarser and/or more irregular foam structure was rated as "o" and a very coarse foam structure unsuitable for technical purposes was rated as "-".

C. Examples

The composition of the individual components in the following Tables is expressed in grams.

    ______________________________________                                         Example No. 1       2.sup.a 3    4    5    6                                   ______________________________________                                         Component A                                                                    Sodium waterglass                                                                          400.0   425.0   482.5                                                                               472.5                                                                               447.5                                                                               422.5                               solution 37/40                                                                 Emulgin 02          2.5                                                        Emulgin 05  5.0     5.0     2.5  2.5  2.5  2.5                                 Dichlorodifluoro-                                                                          95.0    57.5    15.0 25.0 50.0 75.0                                methane                                                                        Component B                                                                    Glycerol Tri-                                                                              30.0    32.0    36.0 35.0 33.0 32.0                                acetate                                                                        Nitrogen    1.2     1.2     1.2  1.2  1.2  1.2                                 Carbon dioxide                                                                             --      --      --   --   --   --                                  Pot life at 30      30      25   25   25   30                                  20° C., minutes                                                         Gross density of                                                                           52      50-60   154  131  62   47                                  the air-dry foam                                                               (kg/m.sup.3)                                                                   ______________________________________                                          .sup.a Component A additionally contains 10.0 g of an aqueous acrylic          resin solution (Plexitex .sup.(R))                                       

    ______________________________________                                         Example No. 7      8      9    10    11    12                                  ______________________________________                                         Component A                                                                    Sodium waterglass                                                                          397.5  347.5  249.0                                                                               400   400   400                                 solution 37/40                                                                 Emulgin 02  2.5    2.5    2.0  10    10    10                                  Emulgin 05                                                                     Dichlorodifluoro-                                                                          100.0  150.0  249.0                                                                               90    90    90                                  methane                                                                        Component B                                                                    Glycerol tri-                                                                              30.0   26.0   18.7 30    30    30                                  acetate                                                                        Nitrogen    1.2    1.2    1.2  1.2   1.0                                       Carbon dioxide                                                                             --     --     --   --    1.2   2.2                                 Pot life at 30     30     30   approx                                                                               approx                                                                               approx                              20° C./minutes          30    25    20                                  Gross density of                                                                           52     75     93   48-50 51-74 46-89                               air-dry foam                                                                   (kg/m.sup.3)                                                                   ______________________________________                                    

    ______________________________________                                         Example No.     13      14     15   16   17                                    ______________________________________                                         Component A                                                                    Sodium waterglass                                                                              400     400    400  --   --                                    solution 50/52                                                                 Sodium waterglass                                                                              --      --     --   400  400                                   solution 48/50 (HF)                                                            Sodium waterglass                                                                              --      --     --   --   --                                    solution 37/40                                                                 Emulgin 02                                                                     Emulgin 05      10      10     10   10   10                                    Dichlorodifluoromethane                                                                        90      90     90   90   90                                    (a).sup.1                                                                      (b).sup.2                                                                      (c).sup.3                                                                      Component B                                                                    Glycerol tri-   30      26.6   23.8 26.6 23.8                                  acetate                                                                        Oxalic acid     --      3.4    6.2  3.4  6.2                                   dimethyl ester                                                                 Zinc oxide                                                                     Nitrogen        1.2     1.2    1.2  1.2  1.2                                   Pot life at     (>24h)  420    300  180  90                                    20° C., minutes                                                         Gross density of the                                                                           --      55     63   280  40                                    air-dry foam (kg/m.sup.3)                                                      ______________________________________                                          .sup.1 Acronol 290 D.sup.(R) (styrene/acrylate dispersion)                     .sup.2 Synthomer 6210.sup.(R) (styrenebutadiene dispersion)                    .sup.3 Vinnapas LL521-1.sup.(R) (vinyl acetate copolymer dispersion)     

    ______________________________________                                                               19                                                       Example No.   18      a/b     20    21   22                                    ______________________________________                                         Component A                                                                    Sodium waterglass                                                                            --      --      --    --   --                                    solution 50/52                                                                 Sodium waterglass                                                                            400                                                              solution 48/50 (HF)                                                            Sodium waterglass                                                                            --      390/    390   390  400                                   solution 37/40        390                                                      Emulgin 02                               5                                     Emulgin 05    10      10/10   10    10   5                                     Dichlorodifluoro-                                                                            90      90/90   90    90   90                                    methane                                                                        (a).sup.1             10/20                                                    (b).sup.2                     10                                               (c).sup.3                           10                                         Component B                                                                    Glycerol triacetate                                                                          21.6    29/28   29    29   30                                    Oxalic acid dimethyl                                                                         8.4                                                              ester                                                                          Zinc oxide                               4                                     Nitrogen      1.2     1.2/    1.2   1.2  1.2                                                         1.2                                                      Pot life at   10      35/35   30    35   25                                    20° C., minutes                                                         Gross density of the                                                                         40      130/    122   130  56                                    air-dry foam (kg/m.sup.3)                                                                            130                                                      ______________________________________                                          .sup.1 Acronal 290 D.sup.(R) (styrene/acrylate dispersion)                     .sup.2 Synthomer 6210.sup.(R) (styrenebutadiene dispersion)                    .sup.3 Vinnapas LL521-1.sup.(R) (vinyl acetate copolymer dispersion)     

    ______________________________________                                         Example No. 23      24     25    26   27    28                                 ______________________________________                                         Component A                                                                    Sodium waterglass                                                                          200     200    200   200  200   200                                solution 37/40                                                                 Emulgin 02  5.0                                                                Emulgin 05          2.0    5.0   5.0  5.0   5.0                                Dichlorodifluoro-                                                                          50      50     10    15   20    25                                 methane                                                                        (a).sup.1                                                                      (b).sup.2                                                                      (c).sup.3                                                                      (d).sup.4                                                                      (e).sup.5                                                                      Component B                                                                    Glycerol tri-                                                                              15.0    15.0   15.0  15.0 15.0  15.0                               acetate                                                                        Nitrogen    (f)     (f)    (f)   (f)  (f)   (f)                                Pot life at 20      20     20    20   20    20                                 25° C., minutes                                                         Gross density of                                                                           55      52     130   93   72    52                                 air-dry foam                                                                   (kg/m.sup.3)                                                                   ______________________________________                                          .sup.1 Chloroparaffin 40                                                       .sup.2 Glycerol                                                                .sup.3 Ethylene glycol                                                         .sup.4 Acronal 290D.sup.(R) (styreneacrylate dispersion)                       .sup.5 Plexitex.sup.(R) (acrylic resin solution)                               (f) Adjustment of the nitrogen pressure in container B to 10 bars        

    ______________________________________                                         Example No. 29      30     31    32   33    34                                 ______________________________________                                         Component A                                                                    Sodium waterglass                                                                          200     200    200   200  200   200                                solution 37/40                                                                 Emulgin 02                            1.2   1.2                                Emulgin 05  5.0     5.0    5.0   5.0  2.4   2.4                                Dichlorodifluoro-                                                                          30      35     40    50   50    50                                 methane                                                                        (a).sup.1                                   5.0                                (b).sup.2                                                                      (c).sup.3                                                                      (d).sup.4                                                                      (e).sup.5                                                                      Component B                                                                    Glycerol tri-                                                                              15.0    15.0   15.0  15.0 15.0  15.0                               acetate                                                                        Nitrogen    (f)     (f)    (f)   (f)  (f)   (f)                                Pot life at 20      20     20    20   20    25                                 25° C., minutes                                                         Gross density of                                                                           55      46     51    52   50    55                                 air-dry foam                                                                   (kg/m.sup.3)                                                                   Remarks:                              .sup.6                                                                               .sup.7                             ______________________________________                                          .sup.1 Chloroparaffin 40                                                       .sup.2 Glycerol                                                                .sup.3 Ethylene glycol                                                         .sup.4 Acronal 290D.sup.(R) (styreneacrylate dispersion)                       .sup.5 Plexitex.sup.(R) (acrylic resin solution)                               (f) Adjustment of the nitrogen pressure in container B to 10 bars              .sup.6 Improved stability under load in vertical gaps                          .sup.7  Relatively low water uptake                                      

    ______________________________________                                         Example No.  35      36      37    38                                          ______________________________________                                         Component A                                                                    Sodium waterglass                                                                           200     200     200   200                                         solution 37/40                                                                 Emulgin 02   1.2     1.2     1.2   1.2                                         Emulgin 05   2.4     2.4     2.4   2.4                                         Dichlorodifluoro-                                                                           50      50      50    50                                          methane                                                                        (a).sup.1                                                                      (b).sup.2    5.0                                                               (c).sup.3            5.0                                                       (d).sup.4                    5.0                                               (e).sup.5                          5.0                                         Component B                                                                    Glycerol tri-                                                                               15.0    15.0    15.0  15.0                                        acetate                                                                        Nitrogen     (f)     (f)     (f)   (f)                                         Pot life at  15      10      25    24                                          25° C., minutes                                                         Gross density of                                                                            approx  approx  approx                                                                               approx                                      the air-dry foam                                                                            70      90      80    50                                          (kg/m.sup.3)                                                                   Remarks:     Greater strength                                                                               Improved flow                                                                  behaviour                                         ______________________________________                                          .sup.1 Chloroparaffin 40                                                       .sup.2 Glycerol                                                                .sup.3 Ethylene glycol                                                         .sup.4 Acronal 290D.sup.(R) (styreneacrylate dispersion)                       .sup.5 Plexitex.sup.(R) (acrylic resin solution)                               (f) Adjustment of the nitrogen pressure in container B to 10 bars        

    __________________________________________________________________________     Example No.                                                                              39   40   41   42  43   44                                           __________________________________________________________________________     Component A                                                                    Waterglass                                                                               HK30 37/40PE                                                                             40/42                                                                               43/45                                                                              47/48                                                                               48/50                                        (type)                                                                         Waterglass                                                                               200  200  200  200 200  200                                          (quantity used)                                                                Alkali metal in                                                                          Na   Na   Na   Na  Na   Na                                           the waterglass                                                                 Emulgin 05                                                                               5.0  5.0  5.0  5.0 5.0  5.0                                          Dichlorodifluoro-                                                                        50   50   50   50  50   50                                           methane                                                                        Component B                                                                    Glycerol tri-                                                                            15.0 15.0 15.0 15.0                                                                               15.0 15.0                                         acetate                                                                        Nitrogen  (a)  (a)  (a)  (a) (a)  (a)                                          Pot life at                                                                              20   40   30   45  >60  >60                                          RT, minutes                                                                    Gross density of                                                                         approx                                                                              approx                                                                              approx                                                                              approx                                                                             approx                                                                              approx                                       the air-dry foam                                                                         50   120  80   120 180  230                                          (kg/m.sup.3)                                                                   __________________________________________________________________________      (a) Adjustment of the nitrogen pressure in container B to 10 bars        

    ______________________________________                                         Example No. 45      46      47    48    49                                     ______________________________________                                         Component A                                                                    Waterglass  50/52   28/30   35    40/41 MorsilH                                (type)                                                                         Waterglass  200     200     200   200   200                                    (quantity used)                                                                Alkali metal in the                                                                        Na      K       K     K     K                                      waterglass                                                                     Emulgin 05  5.0     5.0     5.0   5.0   5.0                                    Dichlorodifluoro-                                                                          50      50      50    50    50                                     methane                                                                        Component B                                                                    Glycerol tri-                                                                              15.0    15.0    15.0  15.0  15.0                                   acetate                                                                        Nitrogen    (a)     (a)     (a)   (a)   (a)                                    Pot life at >60     15      15    10    45                                     RT. minutes                                                                    Gross density of the                                                                       >500    approx  approx                                                                               approx                                                                               approx                                 air-dry foam        50      50    160   200                                    (kg/m.sup.3)                                                                   ______________________________________                                          (a) Adjustment of the nitrogen pressure in container B to 10 bars.       

    ______________________________________                                         Example No.  50      51      52    53    54                                    ______________________________________                                         Component A                                                                    Sodium waterglass                                                                           200     200     200   200   200                                   37/40                                                                          Emulgin 05   0.1     0.2     0.5   1.0   2.0                                   dichlorodifluoro-                                                                           30      30      30    30    30                                    methane                                                                        Component B                                                                    Glycerol tri-                                                                               15      15      15    15    15                                    acetate                                                                        Nitrogen     (a)     (a)     (a)   (a)   (a)                                   Gross density of the                                                                        --      85      82    79    72                                    air-dry foam                                                                   (kg/m.sup.3)                                                                   Foam formation                                                                              -       +       +     +     +                                     Foam structure                                                                              -       o       +     +     +                                     ______________________________________                                          (a) Adjustment of the nitrogen pressure in container B to 10 bars        

    ______________________________________                                         Example No.    55       56      57    58                                       ______________________________________                                         Component A                                                                    Sodium waterglass                                                                             200      200     200   200                                      37/40                                                                          Emulgin 05     3.0      4.0     5.0   10.0                                     Dichlorodifluoro                                                                              30       30      30    30                                       methane                                                                        Component B                                                                    Glycerol tri-  15       15      15    15                                       acetate                                                                        Nitrogen       (a)      (a)     (a)   (a)                                      Gross density of the                                                                          56       53      49    55.sup.(b)                               air-dry foam                                                                   (kg/m.sup.3)                                                                   Foam formation +        +       +     +                                        Foam structure +        +       +     +                                        ______________________________________                                          .sup.(a) Adjustment of the nitrogen pressure in container B to 10 bars         .sup.(b) Drastic reduction in the strength of the foam; foam disintegrate      into crumbs                                                              

EXAMPLES 59 TO 64

Component A

200.0 g of sodium waterglass solution 37/40

5.0 g of emulsifier (as indicated below)

50.0 g of dichlorodifluoromethane or

200.0 g of sodium waterglass solution 37/40

5.0 g of emulsifier (as indicated below)

20.0 g of propane/butane (35/65)

Component B

15.0 g of glycerol triacetate

1.2 g of nitrogen

    ______________________________________                                         Example No.                                                                              59           60        61                                            ______________________________________                                         Emulsifier                                                                               Emulgin 02   Emulgin 05                                                                               Elfanol 510                                   (as supplied)                                                                            liquid       liquid    paste                                         Propellent                                                                     CCl.sub.2 F.sub.2 :                                                            Foam formation                                                                           +            +         +                                             Foam stability                                                                           +++          +++       +++                                           Foam structure                                                                           +            +         -                                             Propellent                                                                     Propane/butane                                                                 Foam formation                                                                           +            +         +                                             Foam stability                                                                           +++          +         ++                                            Foam structure                                                                           +            +         +                                             ______________________________________                                    

    ______________________________________                                         Example No.                                                                              62        63           64                                            ______________________________________                                         Emulsifier                                                                               Dehyquart Dehyquart DAM                                                                               Dehyquart LT                                  (as supplied)                                                                            C paste   paste        liquid                                        Propellent                                                                     CCl.sub.2 F.sub.2                                                              Foam formation                                                                           -         +            +                                             Foam stability      +            ++                                            Foam structure      -            +                                             Propellent                                                                     Propane/butane                                                                 Foam formation                                                                           +         +            +                                             Foam stability                                                                           ++        +            ++                                            Foam structure                                                                           -         -            +                                             ______________________________________                                    

The preceding specific embodiments are illustrative of the practice of the invention. It is to be understood however, that other expedients known to those skilled in the art or disclosed herein, may be employed without departing from the spirit of the invention or the scope of the appended claims. 

We claim:
 1. A process for producing in situ foams based on alkali metal silicates characterized in that (A) an aqueous alkali metal silicate solution containing from 0.1% to 2.56% by weight, based on the amount of said alkali metal silicate solution of an emulsifier which is stable to alkalis and which, when mixed with said alkali metal silicate solution, does not produce any increase in viscosity or any precipitations in said alkali metal silicate solution, said emulsifier being selected from the group consisting of adducts of fatty alcohols with ethylene oxide and monoesters of sulfosuccinic acid with tallow fatty acid monoethanolamide, on the one hand and (B) a hardener solution on the other hand are accomodated in separate pressurized containers A and B, prior to use the hardener solution in container B is added to and mixed with the silicate solution in container A in the presence of a propellent gas liquid under high pressure between 0° and 50° C., and on actuation of the discharge valve of container A, an alkali metal silicate foam is discharged.
 2. The process of claim 1 wherein pressurized container A contains a mixture of from 50% to 97% by weight of an aqueous alkali metal silicate solution and from 50% to 3% by weight of said propellent gas liquid under high pressure.
 3. The process of claim 2 wherein the total solids content of said aqueous alkali metal silicate solution is between 25% to 50% by weight and said solution at 20° C. has a density of from 1.25 to 1.60 g/cc and a viscosity of from 10 to 5000 mPa.s.
 4. The process of claim 1 wherein pressurized container A contains a mixture of from 80% to 95% by weight of an aqueous alkali metal silicate solution and from 20% to 5% by weight of said propellent gas liquid under high pressure.
 5. The process of claim 1 wherein said alkali metal silicate is selected from the group consisting of sodium silicate and potassium silicate.
 6. The process of claim 5 wherein the mol ratio of SiO₂ to Na₂ O is between 2:1 to 4:1 and the mol ratio of SiO₂ to K₂ O is between 2.8:1 to 4:1.
 7. The process of claim 6 wherein the total solids content of said aqueous alkali metal silicate solution is between 25% to 50% by weight and said solution at 20° C. has a density of from 1.25 to 1.60 g/cc and a viscosity of from 10 to 5000 mPa.s.
 8. The process of claim 5 wherein the mol ratio of SiO₂ to Na₂ O is between 2.5:1 to 3.5:1 and the mol ratio of SiO₂ to K₂ O is between 3.2:1 to 3.5:1.
 9. The process of claim 5 wherein the total solids content of said aqueous alkali metal silicate solution is between 25% to 50% by weight and said solution at 20° C. has a density of from 1.25 to 1.60 g/cc and a viscosity of from 10 to 5000 mPa.s.
 10. The process of claim 1 wherein the total solids content of said aqueous alkali metal silicate solution is between 25% to 50% by weight and said solution at 20° C. has a density of from 1.25 to 1.60 g/cc and a viscosity of from 10 to 5000 mPa.s.
 11. The process of claim 8 wherein said viscosity is from 50 to 1000 mPa.s.
 12. The process of claim 1 wherein said aqueous alkali metal silicate solution contains compounds being dissolved, emulsified or dispersed therein and being selected from the group consisting of quaternary ammonium compounds, borates, synthetic resins and alkali-compatible organic and inorganic compounds for improving the mechanical strength of the foams.
 13. The process of claim 1 wherein said hardeners are selected from the group consisting of inorganic gelating agents and organic gelating agents.
 14. The process of claim 13 wherein said organic gelating agent is selected from the group consisting of esters of dicarboxylic acids and glycerol esters of lower alkanoic acid having from 2 to 4 carbon atoms.
 15. The process of claim 1 wherein said hardener is glycerol triacetic acid ester.
 16. The process of claim 1 wherein said hardener is a mixture of glycerol triacetic acid ester with an oxide or salt of a polyvalent cation.
 17. The process of claim 16 wherein said polyvalent cation is selected from the group consisting of Zn, Mg and Ca.
 18. The process of claim 1 wherein said hardener solution contains a propellent selected from the group consisting of propellents which are gaseous above 0° C. and mixtures of propellents which are gaseous above 0° C. with propellents which are liquid under pressure at 0° to 50° C.
 19. The process of claim 1 wherein the amount and type of said hardener is so selected that the "pot life" of the mixture of hardener and silicate solution is longer than the time required discharge all of said mixture from said pressurized container A. 